Current methods for preparing fatty acid esters include the reaction of fatty acid with an alcohol under acid catalytic conditions. The reaction requires the removal of water to drive the equilibrium of the reaction in the desired direction. Additionally, some polyhydroxy compounds which are crystalline or have high melting points, such as tris(hydroxymethyl)methylamino ethanesulfonic acid (TES) and bis(hydroxyethyl)amino ethanesulfonic acid (BES) do not mix readily with fatty acids. TES and BES will dissolve in aqueous acid, but the resulting solution is not miscible with liquid fatty acid, and the reaction does not readily proceed. Therefore, this reaction is of limited use in forming fatty derivatives of such water soluble compounds.
Alternatively, esters of fatty acids can be prepared by reacting a fatty acid halide with a polyhydroxy compound in acetonitrile. For example, the tri-oleoyl ester of TES may be prepared by reacting oleoyl chloride and TES in acetonitrile. However, oleoyl chloride is not readily available in the quantities or purity necessary for commercial production of such esters. While it is possible to generate the oleoyl chloride in situ from relatively pure oleic acid and sulfuryl chloride, or other agents suitable for generating an acid chloride from a fatty acid, the process has not been demonstrated on a commercial scale.